An intoxicating and psychoactive cannabinoid found in cannabis. Delta-9-tetrahydrocannabinol is the most well-known cannabinoid in the plant and is capable of inducing a variety of sensory and psychological effects, including mild reverie, euphoria, increased sensory awareness, and some therapeutic benefits. Historically, cannabis has been cultivated for its euphoric and therapeutic effects, which are largely attributed to the THC molecule.

I've finally found a strain with the right THC:CBD ratio for my pain.

This is one of the most THC-heavy strains available.

Delta 9 THC compound

What does THC stand for?

THC stands for delta-9-tetrahydrocannabinol, the main psychoactive ingredient in cannabis. 

What is THC?

The cannabis world almost unanimously defines delta-9-tetrahydrocannabinol (THC) as the most well-known cannabinoid, responsible for the cannabis “high.” This definition, though undeniably complicated by what we know about the effects of other cannabinoids, is mostly accurate.

In recent years, cannabidiol (CBD) has received more attention for its therapeutic potential, but THC is arguably still the most famous (and certainly the most infamous) cannabinoid. And while THC is not solely responsible for the psychoactive effects of cannabis, it is the primary psychoactive component.

How THC works

Understanding how THC works in the body and mind also means understanding the endocannabinoid system (ECS), a system of cannabinoid receptors, lipids, and enzymes that plays a discernible role in maintaining internal regulatory balance. When our bodies achieve this balance, it's called homeostasis. The ECS is present throughout the body, consisting of three main components: “messenger” molecules, or endocannabinoids, that our bodies produce; the receptors these molecules bind to; and the enzymes that break them down. The ECS has several receptors, but the main players are receptors CB1 and CB2. CB1 receptors, found mainly in the central nervous system, activate when THC binds to them, which in turn causes THC intoxication and other cerebral effects.

The relationship between THC and CBD

Cannabidiol (CBD), the other most well-known marijuana compound, binds to both CB1 and CB2 receptors. It doesn't intoxicate like THC, and its anti-inflammatory and pain-relieving effects may be a result of several other receptor pathways. At the molecular level CBD is the inverse agonist to THC's agonist, inducing the opposite cellular response as THC. 

CBD and THC may induce opposite responses, but that doesn't mean they necessarily cancel one another's effects when used together. Rather, CBD appears to improve the therapeutic and enjoyable effects of THC by minimizing the unwanted side effects such as anxiety and a rapid heartbeat.

Several studies have consistently revealed CBD's ability to curb the potentially negative side effects of THC. Studies from 2010 onward have indicated that CBD minimizes THC's negative effects on memory. A 2012 study even demonstrated that cannabis users with higher CBD intake had better recall memory than users whose cannabis had no CBD. Similar results have been found in studies on THC-related anxiety, dependence potential, and paranoia.

Moreover, because of CBD's ability to counteract adverse THC side effects, it enables patients to tolerate higher doses of THC, resulting in better health outcomes.

What are the effects of THC?

You may have heard the term “entourage effect” (or “ensemble effect”, as preferred by some cannabis experts). While the entourage effect typically refers to the way cannabis terpenes enhance the desired outcomes of cannabinoids, we can also use the term to describe the way cannabinoids magnify the effects of one another.

Whole-plant cannabis or cannabis extracts generally have a greater medicinal value than CBD or THC isolates because they contain a full spectrum of cannabinoids and terpenes, each providing a unique contribution to the therapeutic effect, such as anti-inflammation. Some medical cannabis patients may respond more positively to pure CBD or pure THC, but for some medical outcomes like pain relief, THC and CBD may be synergistic.  

High CBD strains

For those who have benefitted from the use of CBD edibles, oil, or other CBD medicines, high-CBD/low-THC cannabis strains may also prove therapeutic. For recreational users susceptible to the paranoia or extreme couch lock associated with too much THC, high-CBD strains may offer a more tempered, yet still adequately potent, experience. CBD is beginning to rival THC in desirability but a CBD-rich strain or whole-plant extract is more likely to offer the added benefit of the entourage effect than a pure-CBD product.

Recreational effects

When it comes to recreational effects, there is no substitute for the THC in marijuana. It remains the most sought-after cannabinoid, and its euphoric effects are the reason for its popularity with cannabis users. 

Most commonly we think of THC as the stuff that gets you “high.” When it comes to recreational effects, THC is certainly the main player. But the cannabis high for which THC is responsible includes a full spectrum of effects. Depending on how your body and brain respond, you may have already experienced one or more of the following THC effects:


Arguably THC's most popular recreational effect, cannabis intoxication can be marked by both its similarities to and differences from the euphoric or intoxicating effects of other substances. Cannabis intoxication is euphoric, absorbing, and typically occupies both body and mind. Unlike alcohol intoxication, cannabis intoxication doesn't increase aggression. In fact, it may even decrease aggression, according to a 2016 study published in the German journal Psychopharmacology.


Depending on dosage and individual reaction, THC can be a potent sedative. In small to moderate doses, or as part of a whole-plant product, THC is often relaxing and sometimes sleep-inducing. Moderate to high doses of THC tend to have a stimulating effect. But again, both the sedative and energizing effects of THC vary from person to person.

Altered consciousness/perception of the world

The altered state of consciousness typically associated with THC is highly valued among cannabis users. Both recreational users and medical cannabis patients have benefited from the way cannabis alters perception, even though THC is far from the only psychoactive component of cannabis. 

Athletic enhancement

While not all athletic activities are conducive to cannabis use, THC may provide certain benefits for athletes. THC's anti-inflammatory and pain-killing properties can improve recovery after workouts or injuries. While there is little evidence to support the ability of THC to directly improve athletic performance, THC's psychoactive effects may provide a different kind of mental resource that enables athletes to get through a tough workout. For instance, the “runner's high” involves activity at the CB1 receptor, so by incorporating THC into an endurance sport, athletes may be boosting this effect.    

Social and sexual enhancement

There are countless THC-heavy cultivars that carry a socially energizing reputation. The market is also seeing an explosion of cannabis-related sexual wellness products, many of which claim to harness THC's ability to increase physical sensitivity and induce a relaxed, fluid mental state. While the effectiveness of these products is unknown, brain imaging studies have shown that cannabis can enhance libido, and it could be a viable therapy for individuals with low sex drive.


Users report wide and complex effects from THC. One of the possible reasons cannabis has been used in religious and spiritual traditions throughout human history is because of the way THC enhances our senses. These same effects may also facilitate a new appreciation of art or more powerful experiences in nature.

Medical uses of THC

THC may be the central progenitor of recreational cannabis effects, but that doesn't mean it isn't also medicinal. In fact, our cultural framing of THC as recreational, arguably reinforced by the growing legal cannabis industry, may have a limiting effect on the way we understand and apply THC medicinally. Whether alone or as part of a whole cannabis product, THC is far from lacking in medicinal value.

Pain relief

A January 2017 review of more than 10,000 studies in humans demonstrates that cannabis is safe and effective for the relief of chronic pain in adults. Pain from tissue damage and inflammation and damage to the nervous system are treatable with cannabis. THC, in particular, is effective as both an anti-inflammatory and neuroprotective antioxidant. THC's ability to relieve pain relies, in large part, on activation of CB1 receptors in a region of the brain critically involved in controlling pain throughout the body. Profound pain relief is more likely to happen if THC can get into the bloodstream, and into this part of the brain.

Appetite stimulation

Most of what we know about THC and appetite stimulation comes out of cancer and AIDS research. Through the development of medical cannabis as a treatment for cancer and AIDS-related weight loss, we learn that THC may stimulate appetite by interacting with appetite hormones such as ghrelin and leptin, which are involved in regulating food intake. Food intake, metabolism, and energy use are very complex processes, so much more research is required to fully understand how THC promotes appetite.


The endocannabinoid system can play an active role in reducing nausea and vomiting. Research, such as a 2011 study published in the British Journal of Pharmacology, has shown THC to be very effective in reducing nausea and vomiting in cancer patients going through chemotherapy.

Muscle spasticity

Several studies have shown cannabis to be effective in treating muscle spasticity associated with multiple sclerosis (MS). THC in particular has shown potential to rapidly decrease the strength and frequency of MS-related muscle spasms, according to a 2007 study published in the British Journal of Pharmacology. A 2013 study published in the Journal of Neurology found THC may also be effective in treating neuropathic pain associated with MS.

Addiction treatment

Although THC is itself a rewarding substance, it may have some potential to reduce the abuse potential of other substances. In animal models, THC has been shown to diminish the consumption of heroin. Similarly, in humans, whole plant cannabis and THC appear to increase the likelihood that an individual will remain in treatment for opioid use disorder. One theory is that THC reduces individuals' motivation to consume other rewarding substances. 

Beyond these pharmacological effects, cannabis and/or THC may provide additional harm-reduction benefits, such as giving individuals with substance use disorder a non-lethal intoxicating alternative to more dangerous drugs. Of course, the best treatment for addiction is prevention, and there is promising evidence that cannabis may prevent other drug abuse entirely. For instance, when a state passes a medical cannabis law, alcohol sales drop by an average of 15%.


Cannabis users tend to have lower body mass index (BMI), lower rates of fatty liver disease, and lower rates of diabetes than individuals who do not use cannabis. Although it is unclear how much of cannabis' other constituents influence these effects, animal studies have verified that THC plays a key role in the prevention of diet-induced obesity.

Endocannabinoid deficiency

The theory of endogenous cannabinoid deficiency is relatively new; essentially, it is a condition where the body doesn't produce enough of its own cannabinoids, resulting in imbalance in many homeostatic processes such as pain regulation and digestion. There is a compelling argument for a dysfunctional endocannabinoid system in diseases such as migraine, irritable bowel syndrome, and fibromyalgia. It is unknown if endocannabinoid deficiency is genetically inherited, or it is a result of illness or mental distress. Because THC and whole-plant cannabis alleviate the symptoms of these diseases, it makes sense that cannabinoids may be making up for endocannabinoid deficiencies in the body.

Side effects and warnings

THC is a potent cannabinoid and has the undeniable potential to produce adverse side effects. Keep in mind that every person's response to THC and other cannabis compounds is influenced by their unique endocannabinoid system. For instance, scientists have discovered nine variations of the CB1 receptor gene, which opens the door for varied responses to THC. In other words, not everyone will experience the same side effects, or the same level of adverse side effects, associated with THC.


This may be THC's most desirable, and certainly most sought-after quality, but it may also cause unpleasant, if only temporary, physical and mental impairment. THC intoxication isn't dangerous in and of itself, but it can impair a user's ability to perform certain tasks safely. Users shouldn't drive while under the influence of THC.

Rapid heart rate

After consuming a cannabis-based product — flower, concentrate, edible, etc. — users generally experience an increase in heart rate and blood pressure, which may surprise new or infrequent cannabis users. Generally, users who want to avoid a rapid heart rate, or need to for medical reasons (for instance, being on certain kinds of blood pressure regulating medication), can do so by trying low-THC cultivars, or products that are well-balanced by CBD, which offsets this effect.


Because the brain interprets a rapid heart rate as a fight or flight response, a feeling of anxiety or paranoia can frequently accompany a high dose of THC. Users may also want to avoid high-THC cultivars and products if they experience cannabis-related paranoia. Genetics, previous cannabis use, and pre-existing health conditions play a role in determining if THC will produce or alleviate anxiety. It is common for paranoia to diminish over time, as people develop tolerance to the effects of THC. By starting at a low dose, and increasing slowly over time, individuals can overcome paranoia and reap the medical benefits of THC.

Red eyes

Among the most common side effects, and telltale signs, of smoking cannabis is red, bloodshot eyes. After consuming cannabis, it generally takes about five to 10 minutes for users' heart rates to return to normal and for blood pressure to begin to decrease. Lower blood pressure leads to the dilation of blood vessels and capillaries, including ocular capillaries, which results in the eyes turning red. The amount your blood pressure is lowered and how red your eyes become depends on the amount of THC you consume. Cannabis-induced eye redness is a harmless side effect that will typically only last a few hours.


Several studies have shown that CB1-agonists like THC can amplify appetite and hunger signals in the brain, whether by increasing sensory sensitivity (i.e. food tastes better) or increasing your motivation to eat. This side effect is commonly sought out by patients who suffer from cancer, cachexia (wasting syndrome), or other types of appetite impairment.

What to do if you consume too much THC

While it's impossible to have a lethal or even long-term debilitating overdose from cannabis, it is still possible to consume a dose of THC that produces unpleasant, unwanted side effects. A THC overdose may produce symptoms of panic, paranoia, nausea, vomiting, dysphoria, emotional distress, and physical discomfort. Overdose is most likely to occur when a user ingests an edible cannabis product. This is because when THC passes through the digestive system, it is broken down by enzymes in the liver. The liver turns Delta-9 THC into 11-hydroxy THC, which is a far more potent activator of the CB1 receptor. 

Foremost, if you experience intense THC overdose symptoms, try to remain calm. Although the sensation of panic is very common, it is always temporary. THC overdose symptoms can last anywhere from a few minutes to several hours, depending on the amount and method of THC consumption. While waiting for the symptoms to subside, try a calming distraction for your mind such as listening to soothing music or watching TV. Take small sips of water to rehydrate and reduce dry mouth symptoms.

Physicians encourage people experiencing a severe THC overdose to go to the emergency room, where the patient will typically be given a sedative and monitored until overdose symptoms subside. However, most individuals with moderate symptoms can manage an overdose from home with the help of friends or family and a supportive, soothing environment.

Who should avoid THC?

People at risk for psychosis and people with cardiac conditions should generally avoid THC, especially in high doses. Individuals should not consume cannabis where it is not allowed by law. Those under the age of 18 should obtain the advice of a qualified physician before consuming THC. Many jurisdictions require a legal guardian to oversee the administration of medical cannabis to those younger than 18.

The pharmacological history of THC

Delta-9-tetrahydrocannabinol (THC) was first discovered by Raphael Mechoulam and Yechiel Gaoni in 1964 in Israel. Mechoulam and Gaoni were able to identify the THC chemical structure, as well as its psychotropic properties.

In 1965 Professor Friedhelm Korte of the University of Bonn in Germany successfully isolated tetrahydrocannabinolic acid (THCA), a precursor that turns into THC when exposed to heat. That same year, Mechoulam and Gaoni produced the first total synthesis of THC from hashish.

The United States passed the Controlled Substances Act in 1970, which classified cannabis as a Schedule I drug, or a substance with no accepted medical potential and a high potential for abuse, which severely limited the amount of clinical research that could be done on THC and other cannabinoids.

The THC boom

As underground breeders of the 1980s and '90s entered an era of extensive crossbreeding for more potent yields, cannabis cultivars produced higher and higher percentages of THC. Incremental legalization has also played a massive role in creating the high-THC cultivars and cannabis products that most consumers encounter today. According to a 2014 report published by the Society of Biological Psychiatry, the average THC to CBD ratio was 14:1 in 1995, but it jumped to 80:1 by 2014.

THC products


Flower is a general term that refers to the smokable, trichome-covered part of a female cannabis plant. Flower is the most popular form of cannabis due to its versatility - it can be smoked in a pipe or bong or rolled into a joint or blunt.. Cultivars, or cultivated varieties of cannabis, with high THC concentration are the most widely sought after and highly valued on the market. If you're shopping for cannabis flower and mostly interested in getting the right THC percentage for your needs, the following categories may be useful:

Type III – Novice & medical

Cultivars with low amounts of THC, generally popular with patients and newcomers to cannabis. ACDC and Cannatonic are examples of popular cultivars with low THC.

Type II- Functional high/daytime use

Type II cultivars offer a mixed ratio of THC to CBD. Astral Works, Ancient Art, and Goji DC are all examples of cultivars with a THC:CBD ratio that typically results in a “functional high.” These types of cultivars are popular amongst medical users, where THC provides substantial medical benefit, but intoxication is minimal or manageable.

Type I – Functions affected/seasoned user

These potent cultivars contain a minimum of 20% THC and currently make up more than 80% of the cannabis market. These market forces are likely a carryover from the prohibition days, and consumer demand may gradually shift away from these products as less potent varieties become more common.


Cannabis isolates are extractions of a single cannabinoid. Tetrahydrocannabinolic acid (THCA) has become more commonly available in isolate form. THCA isolate only becomes intoxicating when heated, which turns it into active THC.


Concentrates are substances in which the more desirable properties of cannabis, namely cannabinoids and terpenes, have been separated from the rest of the plant matter and distilled or concentrated. Cannabis concentrates are available in a variety of formats and textures, many of which exhibit high concentrations of THC as their main selling point. 

Infused cannabis goods

Any recipe that calls for butter or oil can be readily infused with cannabis. Ingested cannabinoids are processed differently than inhaled cannabis, which can often mean that an edible product is much more intoxicating since cannabinoids enter the bloodstream through the stomach and liver. This also delays the onset of the effects (about 30 to 90 minutes, depending on the person) and extends their duration (from four to eight hours, depending on the dose and the person).

Legality of THC

United States

Cannabis remains a Schedule I drug under federal law, and THC has not been given any clearance as a derivative compound for medical or recreational use. Most states where cannabis is legal, whether it be for medical or adult use, have laws that limit THC content. Most medical marijuana restrict the amount of THC that can be present in CBD products.  


The only countries where adult use and sale of cannabis is federally legal are Uruguay and Canada. Several other countries, including Germany, Greece, Colombia, Peru, the Netherlands, and the United Kingdom have legalized medical marijuana. In many countries where adult use remains technically prohibited, decriminalization laws have made marijuana possession non-criminal.

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The information contained in this site is provided for informational purposes only, and should not be construed as medical or legal advice. This page was last updated on July 14, 2021.